The present invention relates in general to substrate manufacturing technologies and in particular to an optimized activation prevention assembly for a gas delivery system, and methods therefor.
In the processing of a substrate, e.g., a semiconductor wafer, MEMS device, or a glass panel such as one used in flat panel display manufacturing, plasma is often employed. As part of the processing of a substrate (chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, etch, etc.) for example, the substrate is divided into a plurality of dies, or rectangular areas, each of which will become an integrated circuit. The substrate is then processed in a series of steps in which materials are selectively removed (etching) and deposited (deposition) in order to form electrical components thereon.
In a first exemplary plasma process, a substrate is coated with a thin film of hardened emulsion (such as a photoresist mask) prior to etching. Areas of the hardened emulsion are then selectively removed, causing parts of the underlying layer to become exposed. The substrate is then placed in a plasma processing chamber on a substrate support structure comprising a mono-polar or bi-polar electrode, called a chuck. Appropriate etchant source gases (e.g., C4F8, C4F6, CHF3, CH2F3, CF4, CH3F, C2F4, N2, O2, Ar, Xe, He, H2, NH3, SF6, BCl3, Cl2, etc.) are then flowed into the chamber and struck to form a plasma to etch exposed areas of the substrate.
In general, there are three types of etch processes: pure chemical etch, pure physical etch, and reactive ion etch. Pure chemical etching generally involves no physical bombardment, but rather a chemical interaction with materials on the substrate. The chemical reaction rate could be very high or very low, depending on the process. For example, fluorine-based molecules tend to chemically interact with dielectric materials on the substrate, wherein oxygen-based molecules tend to chemically interact with organic materials on the substrate, such as photoresist.
Pure ion etching is often called sputtering. Usually an inert gas, such as Argon, is ionized in a plasma and used to dislodge material from the substrate. That is, positively charged ions accelerate toward a negatively charged substrate. Pure ion etching is both isotropic (i.e., principally in one direction) and non-selective. That is, selectivity to a particular material tends to be very poor, since the direction of the ion bombardment is mostly perpendicular to the substrate surface in plasma etch process. In addition, the etch rate of the pure ion etching is commonly low, depending generally on the flux and energy of the ion bombardment.
Etching that combines both chemical and ion processes is often called reactive ion etch (RIE), or ion assist etch. Generally ions in the plasma enhance a chemical process by striking the surface of the substrate, and subsequently breaking the chemical bonds of the atoms on the surface in order to make them more susceptible to reacting with the molecules of the chemical process. Since ion etching is mainly perpendicular, while the chemical etching is both perpendicular and vertical, the perpendicular etch rate tends to be much faster than in then horizontal direction. In addition, RIE tends to have an anisotropic profile.
However, because plasma processing system operation may also be dangerous (i.e., poisonous gases, high voltages, etc.), worker safety regulations often mandate that plasma processing manufacturing equipment include activation prevention capability, such as a lockout/tagout mechanism. Generally a lockout is a device that uses positive means such as a lock, either key or combination type, to hold an energy-isolating device in a safe position, thereby preventing the energizing of machinery or equipment. For example, when properly installed, a blank flange or bolted slip blind are considered equivalent to lockout devices.
A tagout device is generally any prominent warning device, such as a tag and a means of attachment, that can be securely fastened to an energy-isolating device in accordance with an established procedure. The tag indicates that the machine or equipment to which it is attached is not to be operated until the tagout device is removed in accordance with the energy control procedure. An energy-isolating device is any mechanical device that physically prevents the transmission or release of energy. These include, but are not limited to, manually-operated electrical circuit breakers, disconnect switches, line valves, and blocks. For example, a device is generally capable of being locked out if it meets one of the following requirements: a) it is designed with a hasp to which a lock can be attached; b) it is designed with any other integral part through which a lock can be affixed; c) it has a locking mechanism built into it; or d) it can be locked without dismantling, rebuilding, or replacing the energy isolating device or permanently altering its energy control capability.
Referring now to FIG. 1, a simplified diagram of an inductively coupled plasma processing system is shown. Generally, an appropriate set of gases may be flowed from gas distribution system 122 into plasma chamber 102 having plasma chamber walls 117. These plasma processing gases may be subsequently ionized at or in a region near injector 109 to form a plasma 110 in order to process (e.g., etch or deposit) exposed areas of substrate 114, such as a semiconductor substrate or a glass pane, positioned with edge ring 115 on an electrostatic chuck 116.
A first RF generator 134 generates the plasma as well as controls the plasma density, while a second RF generator 138 generates bias RF, commonly used to control the DC bias and the ion bombardment energy. Further coupled to source RF generator 134 is matching network 136a, and to bias RF generator 138 is matching network 136b, that attempt to match the impedances of the RF power sources to that of plasma 110. Furthermore, vacuum system 113, including a valve 112 and a set of pumps 111, is commonly used to evacuate the ambient atmosphere from plasma chamber 102 in order to achieve the required pressure to sustain plasma 110 and/or to remove process byproducts.
Referring now to FIG. 2, a simplified diagram of a capacitively coupled plasma processing system is shown. Generally, capacitively coupled plasma processing systems may be configured with a single or with multiple separate RF power sources. Source RF, generated by source RF generator 234, is commonly used to generate the plasma as well as control the plasma density via capacitively coupling. Bias RF, generated by bias RF generator 238, is commonly used to control the DC bias and the ion bombardment energy. Further coupled to source RF generator 234 and bias RF generator 238 is matching network 236, which attempts to match the impedance of the RF power sources to that of plasma 220. Other forms of capacitive reactors have the RF power sources and match networks connected to the top electrode 204. In addition there are multi-anode systems such as a triode that also follow similar RF and electrode arrangements.
Generally, an appropriate set of gases is flowed through an inlet in a top electrode 204 from gas distribution system 222 into plasma chamber 202 having plasma chamber walls 217. These plasma processing gases may be subsequently ionized to form a plasma 220, in order to process (e.g., etch or deposit) exposed areas of substrate 214, such as a semiconductor substrate or a glass pane, positioned with edge ring 215 on an electrostatic chuck 216, which also serves as an electrode. Furthermore, vacuum system 213, including a valve 212 and a set of pumps 211, is commonly used to evacuate the ambient atmosphere from plasma chamber 202 in order to achieve the required pressure to sustain plasma 220.
Since it is not uncommon to have over seventeen different gases coupled to a single plasma processing system, manufactures generally configure their gas delivery systems in high density flow component configurations called “gas sticks,” which may themselves be constructed in the form of a manifold assembly (i.e., stainless steel, etc.) attached to a substrate assembly. A gas flow control component generally needs only be attached to the manifold assembly on one side to complete the gas flow channels that are drilled into the manifold assembly itself.
Referring now to FIG. 3, a simplified diagram of gas stick is shown. In a common configuration, a gas cylinder (not shown) is coupled to an inlet valve 302, which allows an operator to shut off any source gas flow into the stick. In some configurations, inlet valve 302 is manually operated. In other configurations, inlet valve 302 is pneumatically operated. That is, inlet valve 302 is operated by a compressed gas, such as compressed air. In addition, although as previously stated, it is often mandated that plasma processing systems have lockout/tagout functionality, it is not generally common to integrate lockout/tagout functionality into inlet valve 302 because of space limitations within the gas distribution system.
Inlet valve 302 may be further coupled to regulator/transducer 304 that substantially maintains a constant pressure to mass flow controller 308, which may be attached to primary shutoff valve 312, which generally allows gas flow in the gas stick to be blocked. Optionally, filter 306 is placed between regulator/transducer 304 and primary shutoff valve 312 to remove any particulates that may have entered the gas stream. In addition, a purge valve 310 is generally located between primary shutoff valve 312 and mass flow controller 308. Mass flow controller 308 is generally a self-contained device (consisting of a transducer, control valve, and control and signal-processing electronics) commonly used to measure and regulate the mass flow of gas to the plasma processing system.
Further coupled to mass flow controller 308, and generally not included in the gas stick itself, is a mixing manifold 314 that generally combines the gas flows from each of the appropriate gas sticks and channels the mixed gases into plasma chamber 318 through injector 316.
However, the density of flow components to each other in a gas distribution system also tends to make individual gas stick activation prevention problematic, particularly at a gas stick inlet valve. In a typical configuration, all the plasma gases must generally be turned off and then vented, should an employee wish to physically access the gas distribution system, for example, as part of the tool assembly process, or in order to integrate the plasma processing system with a customer fabrication facility. This venting process may be further aggravated since the plasma gas shutoff for the gas feed into the inlet valve (prior to entering the gas stick) may not be physically located at the plasma processing system. Hence, an employee may either need to waste time traveling to the plasma gas shutoff location, or the employee may need to coordinate with another employee do the same. It would thus be advantageous to quickly and safely turn off a single gas stick in order to debug a problem or test a gas flow.
In view of the foregoing, there are desired an optimized activation prevention assembly for a gas delivery system and methods therefor.